The present invention relates generally to a system and method used in conjunction with an implantable medical device. More specifically, the present invention relates to a system and method of bridging a transreceiver coil of an implantable medical device during non-communication periods, thereby blocking unwanted magnetic induction signals transmitted from external sources in the absence of a programmer located proximal to the implantable medical device.
Implantable medical device systems known in the art comprise several components, including an implantable medical device, such as a pacemaker or a defibrillator, pacing and/or sensing leads, and a programmer. The leads connect the implantable medical device to the heart of a patient. An implantable medical device, such as a pacemaker or a defibrillator, commonly stores a variety of different types of diagnostic data which assist a clinician or a physician (operator) in evaluating both the operation of the heart of the patient and the operation of the implanted medical device. The specific diagnostic data stored by the implantable medical device includes a variety of information, including a real-time event recording of pacing events.
The programmer of the implantable medical device system is a microprocessor-based device which is a stand-alone unit commonly located at a hospital or within a physician""s office. The operator positions the programmer proximal the implantable medical device. The programmer is capable of communicating with the implantable medical device and displaying information on a display screen. Depending upon the specific programmer, the programmer may be capable of reading information from and transmitting information to the implantable medical device. Other programmers are only capable of monitoring or receiving information from an implantable medical device, without the capability of transmitting information to the implantable medical device. The programmer of the implantable medical device system provides multiple functions, including assessing lead performance during a pacemaker or a defibrillator implantation, receiving feedback information from the implantable medical device for use by the operator, and, depending upon the specific programmer, programming the implantable medical device.
An analyzer, which is sometimes a sub-component of the programmer and sometimes an individual component, is also a microprocessor-based device. The analyzer assists the operators in assessing the electrical performance of a pacing lead system used in conjunction with an implantable medical device system. The analyzer utilizes the programmer as a control and display platform.
There are numerous instances in which diagnostic data must be monitored during an adjustment procedure or must be retrieved from the implantable medical device and displayed on the display screen of the programmer. For example, during a routine follow-up visit of the patient to a clinic, it is often necessary to retrieve information related to the implantable medical device or the patient. Second, during a visit to a clinic, a physician may want to perform a series of tests on the patient and view a variety of information related to the implantable medical device and the patient. Third, during a medical procedure on the patient unrelated to the implantable medical device, it may be necessary to monitor and/or adjust various parameters of the implantable medical device prior to the medical procedure to ensure adequate performance of the implantable medical device during the unrelated medical procedure.
Implantable medical devices and programmers communicate with each other by means of an inductive transreceiver coil located within the programmer and an inductive transreceiver coil located within the implantable medical device. In addition, the implantable medical device includes a programmer detection system which detects the presence of a programmer in proximity to the implantable medical device. For example, the programmer detection system is in a first state when a programmer is not proximal to the implantable medical device. However, when a programmer is located proximal to the implantable medical device, the programmer detection system changes from the first state to a second state. With the programmer detection system in the second state, indicating the presence of a programmer proximal to the implantable medical device, a communication system within the implantable medical device is permitted to communicate with the programmer via the inductive transreceiver coils as previously discussed.
The patents listed in Table 1 are examples of different systems and methods utilizing a transreceiver coil within an implantable medical device.
All patents listed in Table 1 above are hereby incorporated by reference herein in their respective entireties. As those or ordinary skill in the art will appreciate readily upon reading the Summary of the Invention, Detailed Description of the Preferred Embodiments, and claims set forth below, many of the devices and methods disclosed in the patents of Table 1 may be modified advantageously by using the teachings of the present invention.
One disadvantage of prior art implantable medical devices relates to external alternating current (AC) magnetic fields radiating from various sources, such as anti-theft systems used within businesses, shops, or libraries used to prevent goods from being removed from the business without properly paying for or checking out the goods. These anti-theft systems produce dynamic AC magnetic fields between two sources, such as two gates located on either side of an exit path. In many retail businesses or shops, items for purchase include a magnetic device secured to the item. The magnetic device is removed once the item has been purchased. If the magnetic device is not removed prior to exiting the shop or business, the AC magnetic field between the two sources (gates) sense the presence of the magnetic device. Most often, an audio and/or visual alarm is triggered, inferring that the item was removed from the business or shop without proper payment or that the magnetic device was not properly removed at the time of purchase.
Another method of protecting goods is a tag that consists of a printed inductive coil (L) in parallel with a capacitor (C). The tag is detected by gates near the exit of shops due to the specific frequency of the magnetic field produced by the gates. The tag can be made inoperative by a large magnetic field produced by an apparatus near the paying station, which destroys the parallel L, C connection.
The AC magnetic fields transmitted between the two sources do not interact with the communication system of the implantable medical device since they do not have the proper syntax. However, these dynamic AC magnetic fields do produce an undesired load or unintentional drain on the power supply of the implantable medical device due to the external AC magnetic field acting on the inductive transreceiver coil of the implantable medical device. Depending upon the strength of the AC magnetic field and the length of time that the AC magnetic field is acting upon the inductive transreceiver coil of the implantable medical device, the implantable medical device will enter a reset state or mode. The implantable medical device will no longer pace the heart of the patient or sense parameters from the heart of the patient. This may cause the patient to go into cardiac arrest. Once the external AC magnetic field is no longer acting on the implantable medical device, the implantable medical device resumes normal operation, such as pacing and sensing.
Therefore, there is a need for a system which will prevent unwanted AC magnetic fields transmitted from external sources from disrupting electrical circuitry, including the power supply, within an implantable medical device. However, the system should permit desired communications between the implantable medical device and a programmer when the programmer is located in proximity to the implantable medical device.
The present invention overcomes the disadvantages of the prior art by providing a method of and an apparatus for communicating with a programmer located in proximity to the implantable medical device while preventing unwanted magnetic signals transmitted from other external sources from disrupting electrical circuitry within the implantable medical device.
The present invention has certain objects. That is, the present invention provides solutions to certain problems existing in the prior art such as: (a) an inability to prevent unwanted AC magnetic fields transmitted from an external source from disrupting electrical circuitry within an implantable medical device; (b) an inability to prevent unwanted AC magnetic fields detected by an inductive transreceiver coil of an implantable medical device from draining a power supply of the implantable medical device; (c) an inability for an implantable medical device to continue pacing and sensing the heart of a patient due to an unwanted AC magnetic field acting upon an inductive transreceiver coil of the implantable medical device; (d) an inability to short out an inductive transreceiver coil at all times other than when an external programmer is detected in proximity to an implantable medical device; (e) an inability to provide a short circuit in parallel with an inductive transreceiver coil when a programmer is not detected in proximity to an implantable medical device; and (f) an inability to provide an open circuit in parallel with an inductive transreceiver coil when a programmer is detected in proximity to an implantable medical device.
The system and method of the present invention provides certain advantages, including: (a) the ability to prevent unwanted AC magnetic fields transmitted from an external source from disrupting electrical circuitry within an implantable medical device; (b) the ability to prevent unwanted AC magnetic fields detected by an inductive transreceiver coil of an implantable medical device from draining a power supply of the implantable medical device; (c) the ability for an implantable medical device to continue pacing and sensing the heart of a patient by blocking unwanted AC magnetic fields acting upon an inductive transreceiver coil of the implantable medical device; (d) the ability to short out a inductive transreceiver coil at all times other than when a programmer is detected in proximity to an implantable medical device; (e) the ability to provide a short circuit in parallel with an inductive transreceiver coil when a programmer is not detected in proximity to an implantable medical device; and (f) the ability to provide an open circuit in parallel with an inductive transreceiver coil when a programmer is detected in proximity to an implantable medical device.
The system and method of the present invention has certain features, including a switching device connected in parallel with an inductive transreceiver coil of the implantable medical device. The switching device is connected to a programmer detector of the implantable medical device. If the programmer detector detects the presence of a programmer in proximity to the implantable medical device, the switching device is opened, thereby creating an open circuit (high impedance path) in parallel with the inductive transreceiver coil. The implantable medical device can communicate with the programmer via the inductive transreceiver coil. However, if the programmer detector does not detect the presence of a programmer in proximity to the implantable medical device, the switching device is closed, thereby creating a short circuit (low impedance path) in parallel with the inductive transreceiver coil.
Another feature of the present invention is that unless and until the programmer detector of the implantable medical device detects the presence of a programmer proximal to the implantable medical device, any signals received by the inductive transreceiver coil from any external source do not affect the remaining portions of the implantable medical device. More specifically, a power source of the implantable medical device is not drained due to external AC magnetic field acting upon the inductive transreceiver coil. An implantable medical device with a drained power source will no longer pace the heart of the patient or sense parameters from the heart of the patient. This may cause the patient to go into cardiac arrest.
Another feature of the present invention is the activation of an electrical device electrically coupled in parallel with the inductive transreceiver coil, thereby creating a short circuit in parallel with the inductive transreceiver coil due to the lack of detection of a programmer located in proximity to the implantable medical device. The electrical device is deactivated during detection of the presence of a programmer in proximity to the implantable medical device.
Yet another feature of the present invention is a switching device connected in parallel with the inductive transreceiver coil which blocks unwanted AC magnetic fields transmitted from an external source from interacting with a communications system within the implantable medical device in the absence of a programmer located in proximity to the implantable medical device. The switching device permits desired magnetic fields from a programmer to interact with the implantable medical device when the programmer is located in proximity to the implantable medical device, thereby permitting communication between implantable medical device and the programmer.
Other objects, advantages, and features of the invention will become apparent by referring to the appended drawings, detailed description, and claims.